90 gm a/c blowing hot (like heater)?!!

[GoFordBroke]

Yesterday, a/c blows cold enough to hang meat; this morning it blows HOT. I don't hear a door move when the lever is moved between a/c, heat, but the compressor is running fine and the a/c hose is cold. Whuh???

[miamibob]

Blend door stuck in HEAT position? If all else is fine.....

[miamibob]

By the way, AUTO temp control or manual???

[GoFordBroke]

By the way, AUTO temp control or manual???

It's auto. That sounds right; is it a servo issue, a need for lubrication, or are high explosives the answer?

[miamibob]

Also check the sensor behind the dash and heater valve under the hood (attached to a heater hose).

[sly]

it may be the servo... it'll be electric IIRC. Typically the problem is that it strips out the shaft that connects to the blend door or the hole in the blend door. Sometimes it even breaks the blend door shaft (it's all plastic). The problem is that you pretty much have to take the dash down to get at the damn thing to fix it.

[GoFordBroke]

Yesterday I threw it into defrost; I believe it is stuck there - or thereabouts - hence the heat. If I could "urge" it to move, I believe it would free up and operate again. Any way to employ the judicious application of force to unstick the sumbitch? Can I get a hand (or anything else) on that door, or something connected to it? If anyone has ever erred with linkages and fabricated one that that would overtravel and "cam lock", they would understand what I'm trying to describe. The rest of you are probably just wondering what the hell I'm talking about and thinking I've got toys in the attic...

[sly]

does it have the sliders/rotary/digital controls? If it's the slider... the pivot pin probably broke and it's not pulling the internal mechanism back. If it's the rotary... the center of the knob probably cracked and isn't grabbing the switch shaft. If digital... something got broke.

[GoFordBroke]

All sliders. Nothing really happens when I slide the function selector. I assume there is no mechanical connection between the slider and the door mechanism...

[GoFordBroke]

Oh, and thanks for "something got broke..", really? How 'zacly ahm pos' UNbroke it. (Sorry, you know how we southerners talk...)

[GoFordBroke]

I still feel like if I could just once get the door to move a little, all the problems would go away; I don't think whatever electro/vacuum servo is there has enough ass to move the selector dealie - or mobilize whatever network of FoMoCo Oompah-loompahs exists behind the faceplate - past where it is currently, and frustratingly, stuck like Chuck.. bigger'n.., you get it. Is there any place I could get a hand, tool, anything ON the door mechanism to move it/unstick it?

[sly]

on digitals (I don't remember when those started showing up either) it's usually the blend door actuator or the control unit itself that breaks. and since you don't have that one... no worries.

As for the sliders... there's a pivot point that allows the slider to move a mechanical vacuum valve inside the controls... if that's not being moved, then it'll stay in whatever vent it's on. It also will not turn off in this condition. If you can turn it off, it's a blend door/temp slider issue. If you move the slider to off and the blower stays on, then that slider or the controller it connects to is broken.

[gadget73]

not sure if the 1990 uses the vacuum nonsense or the electric nonsense for the blend door. If the air won't change location, that is absolutely a vacuum problem. The older system defaulted to hot defrost with a vacuum fail. The electric system defaults to defrost, but the temperature is run from an electric servo so its not really affected. Check the vacuum lines under the hood to the plastic box where the relays are, the thing in the heater hose with the 2 electric wires and the 2 vacuum lines, and the check valve stuck to the vacuum tree on the firewall.

[GoFordBroke]

Thanks, you guys are terrific.. I'll try to chase it down today. If it doesn't come a turd floater again; there is NO drought in the Big Bend of the Florida panhandle, I can assure you...

[GoFordBroke]

OK, I think - thanks to y'all - I have Isolated it to the temp slider: I heard the guts move in response to the lower slider, but the upper slider seems to be stuck on 85 degrees. How much of the dash needs to come out to see if it is the problem and to replace it? Also, where the hell do I get one? The temp mechanism must interface with fan speed control, right? 'Cuz the fan speed fluctuates when I move the temp slider sometimes...